Try crushing up a few vitamin C tablets, put them in an old sock, and hold them on the stains for a few minutes to see if they will help lift them. There is a procedure that uses ascorbic acid to remove large metal stains, and the vitamin C is the "mini" version of that. You should be able to rig up the sock to your telescoping pole and probably handle this without the scuba tank.

A few years ago I had some rust staining in spots on the bottom of my vinyl pool, and time and normal shocking eventually lifted them, but if the pennies were there for a long time, it will probably take the vitamin C to lift it.

Welcome to the forum!!

Janet